Gas-insulating high-voltage breakers are used in an electrical network carrying high voltages for connecting and disconnecting current having an intensity which ranges from very low inductive and capacitive current through normal load current up to medium and high short-circuit current. It is generally possible with such breakers to interrupt short-circuit currents in the region of 50 kA or above in a voltage range of up to several hundred kV.
A gas-insulated high-voltage circuit breaker of the type mentioned above contains two arcing contacts, which are capable of moving relative to one another along an axis, an insulating nozzle, a heating volume for accommodating quenching gas, a heating channel, and an overpressure valve. With this breaker, the pressure of the quenching gas is determined by the energy of a switching arc which is formed when the breaker opens and generates arcing gas, and the heating channel opens out, with axial alignment, into the heating volume. At the same time, the heating channel connects an arc zone, which is delimited axially from the two arcing contacts and radially with respect to the insulating nozzle, to the heating volume, and the overpressure valve limits the pressure of the quenching gas by opening a relief duct, which opens out into an expansion space.
In order to quench the switching arc, an insulating gas with good arc-quenching properties is used. The insulating gas is compressed during the disconnection operation and subsequently blows the arc, by acting as a quenching gas, until the arc is extinguished in the zero crossing of the current to be interrupted. A compression device is used as the compression means in this arrangement. The compression device is actuated by the breaker drive and therefore requires drive energy and/or the switching arc itself, whose energy, which is released in the high-current phase of the current to be interrupted, is used for storing hot arcing gases under pressure in the heating volume (the so-called self-blowing principle).
Breakers functioning in accordance with the self-blowing principle do not consume any drive energy and also advantageously guide eroded material of an insulating nozzle into the heating volume. The pressure as well as the temperature in the heating volume increase nonlinearly and virtually quadratically with the current intensity of the arc. In general, a heating flow triggered by the switching arc in the arc zone and the size of the heating volume are matched in optimum fashion to low-level and mid-level currents, since, when matching two high-level currents, the heating flow would otherwise be much too low for low currents and it would not be possible for a sufficiently high quenching gas pressure for successful arc blowing to be built up in the heating volume. When switching high currents, arcing gas with a high pressure and a high temperature can therefore form in the arc zone, whereby the arcing gas subjecting both the insulating nozzle and the heating volume to severe mechanical and thermal loads and at the same time has unfavorable quenching gas properties as a result of the high temperature.
A breaker of the type mentioned at the outset is described in DE 44 12 249 A1. This breaker has a heating volume, which can be expanded elastically by the pressure of the quenching gas, and has a delimiting wall which can be adjusted counter to a restoring force. In the event of the occurrence of high-current arcs, the heating volume is enlarged by movement of the delimiting wall, which makes it possible for more hot quenching gas to be stored in the heating volume. In order to limit the quenching gas pressure resulting in the heating volume, an overpressure valve is provided for very high current intensities. The overpressure valve is arranged in a radially aligned wall of the heating volume and guides the quenching gas above a limit value of the quenching gas pressure via an axially extended relief duct into an expansion space.
A breaker described in DE 198 59 764 A1 has storage means, which serve the purpose of buffer-storing heated gas which is formed during interruption of the current by a switching arc burning in an arc zone in the high-current phase of an alternating current to be interrupted. When the current approaches a zero crossing, the heating effect of the switching arc abates and the heated gas first flows out of a small control volume of the storage means via a channel and a gap into the arc zone. Since the control volume is substantially smaller than a quenching volume of the storage means, the control volume empties much quicker than the quenching volume. As a result, the gas pressure in the control volume drops severely, and a wall which separates the two volumes from one another is moved, which causes a quenching opening to be released and the channel to be sealed. Comparatively cool gas from the quenching volume is then guided through the quenching opening and the gap into the arc zone, in which the cool gas blows the switching arc and expands into an expansion space via a constriction of an insulating nozzle and a constriction of a hollow contact piece.